High-order tracking differentiator based adaptive neural control of a flexible air-breathing hypersonic vehicle subject to actuators constraints

In this paper, an adaptive neural controller is exploited for a constrained flexible air-breathing hypersonic vehicle (FAHV) based on high-order tracking differentiator (HTD). By utilizing functional decomposition methodology, the dynamic model is reasonably decomposed into the respective velocity subsystem and altitude subsystem. For the velocity subsystem, a dynamic inversion based neural controller is constructed. By introducing the HTD to adaptively estimate the newly defined states generated in the process of model transformation, a novel neural based altitude controller that is quite simpler than the ones derived from back-stepping is addressed based on the normal output-feedback form instead of the strict-feedback formulation. Based on minimal-learning parameter scheme, only two neural networks with two adaptive parameters are needed for neural approximation. Especially, a novel auxiliary system is explored to deal with the problem of control inputs constraints. Finally, simulation results are presented to test the effectiveness of the proposed control strategy in the presence of system uncertainties and actuators constraints.     

光电跟踪系统快速捕获时间最优滑模控制技术

针对光电跟踪系统目标的快速捕获过程,本文提出了时间最优滑模控制方法。该控制的滑模面函数为时间最优控制系统状态最优运动轨迹,保证系统状态变量沿着最优轨迹滑动;设计相应的指数趋紧率,使状态变量快速平稳趋近滑模面。以180°、90°、60°阶跃信号为捕获目标进行仿真与实验研究,实验结果为时间最优滑模控制调节时间比时间最优控制和滑模控制分别减小了约43.66%、59.67%,超调量为0,稳态波动量为0,稳态误差减小了约为44.94%和62.34%,与仿真结果相吻合。结果表明该方法调节时间短,超调小,稳态值平稳,稳态误差小,鲁棒性强等优点适合应用于光电跟踪系统目标快速捕获,具有重要的研究与应用价值。     

基于级联滑模控制的高精度光电跟踪与捕获

为了进一步提高光电跟踪系统的目标捕获和跟踪性能,提出了一种基于变增益趋近律的级联滑模控制方法。基于反双曲正弦函数和幂次项设计了新型变增益滑模趋近律,在提高滑模面趋近速度的同时抑制滑模抖振现象;基于变增益滑模趋近律设计速度环和位置环滑模控制器构成级联滑模控制,以提高系统的动态响应性能和鲁棒性,提高系统对目标的捕获能力和跟踪精度。最后,以某球形光电跟踪系统的方位轴作为控制对象,进行了传统级联PI控制和级联滑模控制方法的对比分析。实验结果表明,相比于传统级联PI控制,捕获速度为1(°)/s的目标时,级联滑模控制可以将目标捕获时间减小32%;跟踪等效最大速度为4(°)/s和最大加速度为2(°)/s 2的正弦引导信号,可将跟踪误差RMS值减小31%,采用级联滑模控制可有效提高跟踪系统的控制性能。     

Fuel optimal control of parallel hybrid electric vehicles

A mathematical model for fuel optimal control and its corresponding dynamic programming (DP) recursive equation were established for an existing parallel hybrid electric vehicle (HEV). Two augmented cost functions for gear shifting and engine stop-starting were designed to limit their frequency. To overcome the problem of numerical DP dimensionality, an algorithm to restrict the exploring region was proposed. The algorithm significantly reduced the computational complexity. The system model was converted into real-time simulation code by using MATLAB/RTW to improve computation efficiency. Comparison between the results of a chassis dynamometer test, simulation, and DP proves that the proposed method can compute the performance limitation of the HEV within an acceptable time period and can be used to evaluate and optimize the control strategy. __________ Translated from Journal of Shanghai Jiaotong University, 2006, 40(6): 947–951, 957 [译自: 上海交通大学学报]     

Performance analysis of active disturbance rejection tracking control for a class of uncertain LTI systems

The paper considers the tracking problem for a class of uncertain linear time invariant (LTI) systems with both uncertain parameters and external disturbances. The active disturbance rejection tracking controller is designed and the resulting closed-loop system׳s characteristics are comprehensively studied. In the time-domain, it is proven that the output of closed-loop system can approach its ideal trajectory in the transient process against different kinds of uncertainties by tuning the bandwidth of extended state observer (ESO). In the frequency-domain, different kinds of parameters׳ influences on the phase margin and the crossover frequency of the resulting control system are illuminated. Finally, the effectiveness and robustness of the controller are verified through the actuator position control system with uncertain parameters and load disturbances in the simulations.     

Input-to-state stability of time-varying nonlinear discrete-time systems via indefinite difference Lyapunov functions

In this paper, we propose new sufficient criteria for input-to-state stability (ISS) of time-varying nonlinear discrete-time systems via indefinite difference Lyapunov functions. The proposed sufficient conditions for ISS of system are more relaxed than for ISS with respect to Lyapunov functions with negative definite difference. We prove system is ISS by two methods. The first way is to prove system is ISS by indefinite difference ISS Lyapunov functions. The second method is to prove system is ISS via introducing an auxiliary system and indefinite difference robust Lyapunov functions. The comparison of the sufficient conditions for ISS obtained via the two methods is discussed. The effectiveness of our results is illustrated by three numerical examples.     

Reachable set estimation for Takagi-Sugeno fuzzy systems against unknown output delays with application to tracking control of AUVs

In this paper, we address the problem of reachable set estimation for continuous-time Takagi-Sugeno (T-S) fuzzy systems subject to unknown output delays. Based on the reachable set concept, a new controller design method is also discussed for such systems. An effective method is developed to attenuate the negative impact from the unknown output delays, which likely degrade the performance/stability of systems. First, an augmented fuzzy observer is proposed to capacitate a synchronous estimation for the system state and the disturbance term owing to the unknown output delays, which ensures that the reachable set of the estimation error is limited via the intersection operation of ellipsoids. Then, a compensation technique is employed to eliminate the influence on the system performance stemmed from the unknown output delays. Finally, the effectiveness and correctness of the obtained theories are verified by the tracking control of autonomous underwater vehicles.     

Adaptive tracking control of two-wheeled welding mobile robot with smooth curved welding path

This paper proposes an adaptive controller for partially known system and applies to a two-wheeled Welding Mobile Robot (WMR) to track a reference welding path at a constant velocity of the welding point. To design the tracking controller, the errors from WMR to steel wall is defined, and the controller is designed to drive the errors to zero as fast as desired. Additionally, a scheme of error measurement is implemented on the WMR to meet the need of the controller. In this paper, the system moments of inertia are considered to be partially unknown parameters which are estimated using update laws in adaptive control scheme. The simulations and experiments on a welding mobile robot show the effectiveness of the proposed controller.     

Re-Entry trajectory tracking via an inverse dynamics method

Atmospheric Re-Entry guidance is divided as longitudinal and lateral. This paper proposes a longitudinal reference trajectory and control law using the inverse dynamics method with pseudospectral Legendre method. Application of this method into Re-Entry problem forces a power of calculation time-reduction due to unnecessary of integration or any iteration as well as sufficient accuracy convergence. The used guidance scheme is time-to-go.     

基于自校正控制的空间光通信精跟踪系统设计

针对空间光通信捕获、跟踪、对准(acquisition,tracking,pointing,ATP)系统的精跟踪单元高度复杂、被控对象参数模型难以精确获得、存在慢变化随机干扰的特点,提出采用自校正PID(proportional,integral and derivative)控制来设计精跟踪的控制器,改善了系统动态性能,增强了系统对不确定因素的适应性。采用遗忘因子递推最小二乘法来进行参数辨识,能在线调整适应对象参数的变化,增强了系统的适应性和鲁棒性。通过仿真验证了算法的控制性能和参数辨识效果,算法的实时性也满足系统设计的要求。给出了ATP精跟踪系统的设计框图,进行了2.3 km的精跟踪实验。实验结果表明精跟踪系统采用自校正PID控制有较好的跟踪精度。     

基于模型预测控制的UUV路径跟踪控制研究

水下无人航行器(UUV)的路径跟踪控制是实现UUV多种军、民用途的重要技术基础。针对UUV路径跟踪控制中的欠驱动、非完整约束、模型的非线性,基于非线性连续模型预测控制算法设计了UUV垂直面路径跟踪控制器。建立了垂直面运动模型并基于状态空间模型给出了垂直面预测模型,通过给定性能指标,运用泰勒级数展开与李导数求解出了连续时间状态下的最优控制律,实现了欠驱动UUV路径跟踪控制。通过仿真实验,验证了垂直面路径跟踪控制器设计的有效性。     

Composite disturbance rejection control based on generalized extended state observer

Traditional extended state observer (ESO) design method does not focus on analysis of system reconstruction strategy. The prior information of the controlled system cannot be used for ESO implementation to improve the control accuracy. In this paper, composite disturbance rejection control strategy is proposed based on generalized ESO. First, the disturbance rejection performance of traditional ESO is analyzed to show the essence of the reconstruction strategy. Then, the system is reconstructed based on the equivalent disturbance model. The generalized ESO is proposed based on the reconstructed model, while convergence of the proposed ESO is analyzed along with the outer loop feedback controller. Simulation results on a second order mechanical system show that the proposed generalized ESO can deal with the external disturbance with known model successfully. Experiment of attitude tracking task on an aircraft is also carried out to show the effectiveness of the proposed method.     

DSP-based adaptive backstepping using the tracking errors for high-performance sensorless speed control of induction motor drive

This paper presents a modified structure of the backstepping nonlinear control of the induction motor (IM) fitted with an adaptive backstepping speed observer. The control design is based on the backstepping technique complemented by the introduction of integral tracking errors action to improve its robustness. Unlike other research performed on backstepping control with integral action, the control law developed in this paper does not propose the increase of the number of system state so as not increase the complexity of differential equations resolution. The digital simulation and experimental results show the effectiveness of the proposed control compared to the conventional PI control. The results analysis shows the characteristic robustness of the adaptive control to disturbances of the load, the speed variation and low speed.     

Sliding mode based trajectory linearization control for hypersonic reentry vehicle via extended disturbance observer

This paper proposes a novel hybrid control framework by combing observer-based sliding mode control (SMC) with trajectory linearization control (TLC) for hypersonic reentry vehicle (HRV) attitude tracking problem. First, fewer control consumption is achieved using nonlinear tracking differentiator (TD) in the attitude loop. Second, a novel SMC that employs extended disturbance observer (EDO) to counteract the effect of uncertainties using a new sliding surface which includes the estimation error is integrated to address the tracking error stabilization issues in the attitude and angular rate loop, respectively. In addition, new results associated with EDO are examined in terms of dynamic response and noise-tolerant performance, as well as estimation accuracy. The key feature of the proposed compound control approach is that chattering free tracking performance with high accuracy can be ensured for HRV in the presence of multiple uncertainties under control constraints. Based on finite time convergence stability theory, the stability of the resulting closed-loop system is well established. Also, comparisons and extensive simulation results are presented to demonstrate the effectiveness of the control strategy.     

Real time simulation of nonlinear generalized predictive control for wind energy conversion system with nonlinear observer

In order to make a wind power generation truly cost-effective and reliable, an advanced control techniques must be used. In this paper, we develop a new control strategy, using nonlinear generalized predictive control (NGPC) approach, for DFIG-based wind turbine. The proposed control law is based on two points: NGPC-based torque-current control loop generating the rotor reference voltage and NGPC-based speed control loop that provides the torque reference. In order to enhance the robustness of the controller, a disturbance observer is designed to estimate the aerodynamic torque which is considered as an unknown perturbation. Finally, a real-time simulation is carried out to illustrate the performance of the proposed controller.     

Adaptive fuzzy wavelet network control of second order multi-agent systems with unknown nonlinear dynamics

In this paper, consensus problem is considered for second order multi-agent systems with unknown nonlinear dynamics under undirected graphs. A novel distributed control strategy is suggested for leaderless systems based on adaptive fuzzy wavelet networks. Adaptive fuzzy wavelet networks are employed to compensate for the effect of unknown nonlinear dynamics. Moreover, the proposed method is developed for leader following systems and leader following systems with state time delays. Lyapunov functions are applied to prove uniformly ultimately bounded stability of closed loop systems and to obtain adaptive laws. Three simulation examples are presented to illustrate the effectiveness of the proposed control algorithms.     

基于柔性直流阻尼控制器与附加励磁阻尼控制器协同抑制次同步振荡研究

针对包含模块化多电平换流器型直流输电(MMC_HVDC)的交直流混合输电系统中出现的次同步振荡(SSO)问题,对基于MMC_HVDC的次同步阻尼控制器(MMC_SSDC)与附加励磁阻尼控制器(SEDC)的协同抑制问题进行了研究。首先针对待研究的交直流混合输电系统,设计了MMC_SSDC和SEDC的结构并针对实际算例整定其相位补偿及增益参数;然后分别从理论分析和系统电气阻尼特性的矢量叠加关系方面对MMC_SSDC和SEDC协同抑制策略的可行性进行了研究;最后在PSCAD/EMTDC上搭建模块化多电平换流器为335电平的交直流混合系统时域仿真模型,仿真结果验证了结论的正确性和协同抑制方案的有效性。研究结果表明:MMC_SSDC和SEDC在增加系统电气阻尼的效果上不仅不会相互影响且基本满足矢量叠加关系,利用两者协同抑制SSO的方案是可行的。